Experimental realization of nearly steady-state toroidal electron plasmas

Stoneking, M. R.; Marler, J. P.; Ha, B. N.; Smoniewski, J.
May 2009
Physics of Plasmas;May2009, Vol. 16 Issue 5, p055708
Academic Journal
Electron plasmas with densities of 5×106 cm-3 are trapped in the Lawrence Non-neutral Torus II (LNT II) for times exceeding 1 s. LNT II is a high aspect ratio (R0/a>=10) partially toroidal trap (270° arc, B0=670 G). The m=1 diocotron mode is launched and detected using isolated segments of a fully sectored conducting boundary and its frequency is used to determine the total trapped charge as a function of time. The observed confinement time (≈3 s) approaches the theoretical limit (≈6 s) set by the magnetic pumping transport mechanism of Crooks and O’Neil [Phys. Plasmas 3, 2533 (1996)]. We also present equilibrium modeling and numerical simulations of the toroidal m=1 mode constrained by experimental data. Future work includes the identification of the dominant transport mechanisms via confinement scaling experiments and measurement of the m=2 mode frequency and development of a strategy for making a transition to fully toroidal confinement.


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